1. Field of the Invention
The present invention relates to electrochromic thin-film systems and their components, especially those which are prepared by the sol-gel process.
2. Discussion of the Background
Large numbers of electrochromic thin-film systems are described in the literature for a variety of fields of application and in different combinations of individual components.
For the preparation of the functional oxide layers the methods described hitherto have predominantly been vacuum methods, such as thermal evaporation, sputtering or CVD, and also spray pyrolysis and electrochemical deposition methods. However, these processes are unsuitable and/or too cost-intensive for the production of homogeneous coatings with a large surface area. In recent years, some attempts have been made to produce such systems by sol-gel processes, since these processes are notable for a great scope variation and, owing to the avoidance of vacuum technology, by substantially lower costs for the production of homogeneous coatings of large surface area. However, the systems described in the literature to date are not yet entirely satisfactory.
In particular, in the case of electrochromic oxide layers, especially of tungsten oxides and molybdenum oxides, the fact that the oxides in a freshly prepared thin-film system are initially free from alkali metal ions means that these systems have to be operated for a relatively long period before, gradually, the desired insertion disequilibrium by incorporation of alkali metal ions from the electrolyte ion reserve. This leads to initial impairment of function.